In the case of airbags, depending on the interior dimensions and the contour of the adjacent surfaces (especially the instrument panel) airbags having different characteristics are employed. In the case of very plane surfaces and simple contours the so-called two-dimensional airbags adapted to be manufactured at lower cost are used. In the case of these airbags it is possible to manufacture the airbag of a one-piece cloth part which is then folded and sewed at the margins which are adjacent by folding. Those two-dimensional airbags are suited for rather simple contours, however, as mentioned already. What is important with the airbag is the fact that it can contact an adjacent vehicle part and can be backed by the same in the case of impact of the occupant.
It is moreover desirable that the seams are not thermally overloaded.
Hereinafter the term “seam” is preferably directed to margins which are in fact sewed up to each other, wherein this is not restrictive, however, as there already exist seams that are welded or glued to each other and they are equally supposed to be understood by “seam”.
U.S. Pat. No. 5,316,337 provides an example of a so-called two-dimensional airbag.
Moreover, there are also the so-called three-dimensional airbags in which the airbag has a more complex outer contour in the inflated state and consists of plural individual parts sewed together, especially of two sidewalls and a strip-shaped circumferential central part connecting the sidewalls to each other so that kind of a roll is resulting which need not be circular-cylindrical, however, but may have any shapes depending on the geometry of the sidewalls. It is more difficult to sew such three-dimensional airbags, as the margins to be sewed up are not placed on top of each other by simply folding the airbag cloth.